Transport and reaction at endothelial plasmalemma: distinguishing intra- from extracellular events

The pulmonary endothelium is a chemical reactor that modifies blood composition in several ways, including reduction of the oxidized forms of certain redox active substances in the blood. The physiological functions of the transplasma membrane electron transport systems involved in the latter are not fully understood, but an argument is made that they are involved in antioxidant defense. In addition, the experimental approaches used to characterize the process, including studies at whole organ, cell culture, and subcellular levels, along with the use of mathematical modeling, may be representative of the physiome concept wherein a goal is the integration of information obtained at all levels of biological organization. In this article, separation of intra- and extracellular events involved in the disposition of redox active probes within the lungs is the particular example.